In Minnesota, Santorum captured 45 percent of the vote, with Rep. Ron Paul in second at 27 percent and former Massachusetts Gov. Mitt Romney a distant third with 17 percent. In Missouri, Santorum won 55 percent of the vote to Romney’s 25 percent. In the Colorado caucuses, Santorum beat Romney by five points.

Rick Santorum

In his victory speech in Missouri, Santorum declared, “Conservatism is alive and well in Missouri and Minnesota,” and took a dig at Republican frontrunner Mitt Romney.

“Your votes today were not just heard loud and wide across the state of Missouri and Minnesota, but they were heard loud and louder all across this country, and particularly in a place that I suspect may be in Massachusetts they were heard particularly loud tonight,” Santorum said.

He added that he is not the conservative alternative to Romney, but the “conservative alternative to Barack Obama.”

Jerame Davis, executive director of the National StonewallDemocrats, said Santorum’s wins are evidence the “non-Romney wing” of the GOP is still the dominant force in the party and “yet more proof that Republicans can’t stand Mitt Romney.”

“Conservative Republicans may love Rick Santorum’s unwavering sanctimony and seething anti-intellectualism, but his narrow, regressive brand of politics will turn off independents and even many moderate Republicans,” Davis said.

R. Clarke Cooper, executive director of the Log Cabin Republicans, dismissed Santorum’s wins because he said the candidate can’t unify the Republican Party.

“As former RNC chairman Gov. Haley Barbour has observed, ‘purity is the enemy of victory,’” Cooper said “The ability to secure the vote of the general electorate is necessary to succeeding as the Republican nominee. The divisive Rick Santorum is not capable of winning a general election and will not be the Republican nominee.”

The wins for Santorum in Minnesota and Missouri are largely symbolic. Missouri isn’t awarding any delegates at the Republican National Convention. Minnesota and Colorado will award their delegates at a later date.

Still, Santorum’s victory is sure to be a thorn in the side of frontrunner Romney, who last week seemed poised to claim the Republican nomination after his victory in the Nevada caucuses. Observers say Tuesday’s results raise questions about whether Romney can close the deal and win the Republican nomination.